Your sense of smell is like a superpower. Dr. Alan Hirsch of the Smell and Taste Treatment and Research Foundation explains how you can make the most of it. Your nose is always working, even when you're asleep. It can affect your mood, your ability to concentrate, and even your sense of time and space. The kicker? A lot of the time, you may not even know you're being affected! To learn more about smell, we sat down with Dr. Alan Hirsch, a neurologist and psychiatrist who specializes in the treatment of smell and taste loss. Dr. Hirsch is Neurological Director of the Smell & Taste Treatment and Research Foundation in Chicago, where he conducts in-depth studies of the chemosensory system and its impact on virtually all aspects of life: behavior, emotions, mood and human interaction, and even learning speed. He has also written numerous books including "Scentsational Weight Loss", "Scentsational Sex", and "What Flavor Is Your Personality?" Studies discussed: Minnesota Multiphasic Personality Inventory (MMPI) Millon Clinical Multiaxial Inventory (MCMI) Beck Depression Inventory (BDI) Zung Self-Rating Anxiety Scale (SAS) Further materials from Dr. Hirsch: Smell & Taste Treatment And Research Foundation, Ltd. Dr. Hirsch's Amazon Author Page "What Flavor is Your Personality? Discover Who You Are by Looking at What You Eat" "Scentsational Weight Loss: At Last a New Easy Natural Way To Control Your Appetite" "Scentsational Sex: The Secret to Using Aroma for Arousal" Follow Curiosity Daily on your favorite podcast app to get smarter withCody Gough andAshley Hamer — for free! Still curious? Get exclusive science shows, nature documentaries, and more real-life entertainment on discovery+! Go to https://discoveryplus.com/curiosity to start your 7-day free trial. discovery+ is currently only available for US subscribers.
Your sense of smell is like a superpower. Dr. Alan Hirsch of the Smell and Taste Treatment and Research Foundation explains how you can make the most of it.
Your nose is always working, even when you're asleep. It can affect your mood, your ability to concentrate, and even your sense of time and space. The kicker? A lot of the time, you may not even know you're being affected!
To learn more about smell, we sat down with Dr. Alan Hirsch, a neurologist and psychiatrist who specializes in the treatment of smell and taste loss. Dr. Hirsch is Neurological Director of the Smell & Taste Treatment and Research Foundation in Chicago, where he conducts in-depth studies of the chemosensory system and its impact on virtually all aspects of life: behavior, emotions, mood and human interaction, and even learning speed. He has also written numerous books including "Scentsational Weight Loss", "Scentsational Sex", and "What Flavor Is Your Personality?"
Studies discussed:
Further materials from Dr. Hirsch:
Follow Curiosity Daily on your favorite podcast app to get smarter with Cody Gough and Ashley Hamer — for free! Still curious? Get exclusive science shows, nature documentaries, and more real-life entertainment on discovery+! Go to https://discoveryplus.com/curiosity to start your 7-day free trial. discovery+ is currently only available for US subscribers.
Full episode transcript here: https://curiosity-daily-4e53644e.simplecast.com/episodes/how-your-sense-of-smell-is-like-a-superpower
CODY GOUGH: I'm curious. Why is smell so important, and why should people care about smell?
ALAN HIRSCH: Smell is so important because it impacts upon us all the time, whether we recognize it or not. The quickest way to affect somebody's mood state or emotions quicker than any other sensory modality is with smell.
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CODY GOUGH: Hey, I'm Cody Gough from curiosity.com. Today we're going to learn about the way that smell can affect our moods, and our perception, and even our relationships. Every week we explore what we don't know because curiosity makes you smarter. This is the Curiosity podcast.
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Your nose is always working. Even when you're asleep it sends signals to your brain that can totally affect your mood, your concentration, your sense of time and space, basically, everything. And what's weird is that you may not even know you're being affected. So to learn more about this, I spoke with Dr. Alan Hirsch, chief neurologist and psychiatrist at the Smell and Taste Treatment and Research Foundation in Chicago.
ALAN HIRSCH: So unlike the other senses, vision or hearing where you consciously recognize something, smell acts as a pure emotional sense. For instance, you see a picture of a cow, or a tree, or a horse, you identify it. You decide if you like it or not, and then you go from there. With smell, it's the exact opposite. You smell a smell and immediately you decide I like it or I don't like the smell. So it's a pure emotional sense. Even before you identify what the smell is, you've already decided if you like it.
So the quickest way to affect somebody's mood, state, or emotions, quicker than any other sensory modality, is with smell. You'll smell a bad smell, and it'll make you feel angry or it will make you feel sad. You smell a pleasant smell, and you'll be happier. So all the time, everywhere we go, smells are impacting upon us in all sorts of different ways, even unconsciously.
So let me give you an example of how we know this. We've been studying this over the last 25, 30 years looking at how smells can impact upon people's behavior. And one of the things we did is we looked at brainwaves. And we looked at brain waves of medical students. And what we found is that in the presence of different odors, you could actually cause changes in brainwaves.
So for instance, lavender tends to increase alpha waves in the back of the head, which is associated with a more relaxed state. Whereas, jasmine increases beta waves in the front of the head and the EEG associated with more awake and alert state. So you can actually cause somebody to be more awake and alert, or more relaxed based on the odor that's present.
CODY GOUGH: OK, there's a lot to unpack. First of all, you mentioned that you can get an emotional response the fastest with the nose. What about music? If something's too loud, doesn't that cause pain?
ALAN HIRSCH: Well, that's right. And music will cause pain and that will cause a response. And you can cause a response with a strong irritant odor as well. So for instance, what happens when you pass out? They take you and give smelling salts under the nose to wake you up. Well, that's an example where smell is inducing-- directly affecting the reticular activating system, that part of the brain that makes us awake and alert. And what it does is it stimulates the trigeminal nerve or the irritant nerve. That's the nerve that makes you cry when you cut an onion, for instance. And so it can make you more awake.
And similarly, not only can odors cause you to be more awake, they can also cause you to be more sleepy. So for instance, when we studied the effects of odors on sleep, we found that different aromas can actually cause you to fall asleep faster. When we look at something called sleep onset REM latency in the presence, for instance, of lavender, people tend to fall asleep faster. Now, that's not true for everybody.
For instance, if you dislike lavender, it doesn't have this positive effect. And possibly what happens is odors become associated with emotions and associated with people, and strong emotional experiences. So for instance, let's say you had a girlfriend, or a boyfriend, or somebody who wore the smell of lavender and you now dislike that person. When you smell that smell it induces that same strong negative emotion, and so it prevents you from going to sleep.
CODY GOUGH: Now, wait a second. So then doesn't that make all of these smells and how they affect your brain a little bit subjective?
ALAN HIRSCH: Well, what happens is there's strong individual variation from person to person. However, what we found is you can-- actually you can show changes in brain waves with levels of odor that are so low, the medical students were unaware that an odor was present. So they-- not even-- they could not even recognize an odor was present, yet we were able to show changes in brain waves suggesting that at some level odors are working in an unconscious basis.
And so you can, in theory, impact upon people in a subliminal way based on smells. And so you go into a room and there's an odor there and it may make you more angry or maybe make you happier, and you don't even recognize why that's the case.
CODY GOUGH: So lavender has a specific scientific effect, generally. But if I have an ex-girlfriend that used to wear a lot of lavender then suddenly I have a negative association, but that scientific effect is still going to impact me?
ALAN HIRSCH: Well, at least, it consciously-- when you're conscious of it you'll respond in a negative way. But if you're not conscious of it it'll still induce the same positive impact. So what happens is we can learn to like things that are negative for us. For instance, let me give you a good example, hot Chili peppers. Hot Chili peppers induce a trigeminal response. It's capsaicin. And so on the tongue it induces , pain and it causes actually destruction of taste buds.
ASHLEY HAMER: Hey, Cody.
CODY GOUGH: Hey, Ashley Hamer, one of our editors, who's going to pop in from time to time with a little fast fact for us.
ASHLEY HAMER: That is right. I wanted to talk about capsaicin, which is the compound that gives chili peppers their heat. That trigeminal response he's talking about involves capsaicin effect on the trigeminal nerve, the one responsible for sensations in your mouth and face, like heat, tingling, and pain.
ALAN HIRSCH: And people will cry in response to it. And they'll turn red-- be red, and they'll be sweaty. Yet people love them, even though it's inducing pain. So what we've done is we've-- over years, through experience, we've learned to like something that is intrinsically negative to an individual. Another good example would be coffee. When you drink coffee, coffee initially is very bitter and people would naturally avoid it. But what happens is over time they learn that they get a positive response from the caffeine or a social response for it, and they begin to use it more and more.
So we-- another great example is cigarette smoke. Cigarette smoke initially has a strong aversive response, yet over time people learn to like it and hence use it. So we can overcome an underlying physiological response through learning.
CODY GOUGH: Even beer.
ALAN HIRSCH: Even beer. Now, beer is another great example. Because actually for some individuals beer tastes good. For some individuals beer tastes horribly bitter, and it has to do with the number of taste receptors they have for bitter. And so those who have very strong bitter taste receptors will avoid beer. Where those without it are more likely to drink it. So there's all sorts of things that go on within our body that physiologically affect us, yet we overcome it because of cognitive reasons. We want to be social, or we've learned over time.
I guess another great example. If you go on a roller coaster. What happens if we go on a roller coaster? You get scared. You're scared. Oh my goodness, I'm really scared. You go on the roller coaster. You just scream. The first thing you do when you get off it is you want to go again. Because in the roller coaster you've survived death in this one episode, and therefore is giving you that thrill. You get that same thrill, that same adrenaline rush with for instance, hot chili pepper.
CODY GOUGH: You survive the chili pepper.
ALAN HIRSCH: Exactly. There are other reasons why people use Hot Chili pepper. For instance, one of the theories is that it causes an increase in salivation. So in places where it's dry in the desert people learn to use it. Or possibly what happens is it may be the equivalent of a coffee. Coffee is something for an adult and hot chili pepper is something that an adult learns to use. Or possibly it's because hot chili peppers induce release of endorphin on the tongue. And endorphins act inhibit pain. So it's giving a little morphine on the tongue. So all of these could be reasons why it's used and it's so popular today.
CODY GOUGH: And when you're talking about chili peppers, you're talking about something spicy. But most of that you detect after you've put it in your mouth and you're tasting it. So I'm guessing taste and smell are extremely closely related.
ALAN HIRSCH: Well, you're exactly right. As a matter of fact, 90% of the time when we talk about taste, we really mean smell. So for instance, if you hold your nose and eat chocolate it tastes just like chalk. It has no taste at all. If you hold your nose, and eat a carrot and potato, you can't taste the difference. Or even an apple and an onion. When you were a kid and you had to eat spinach, what you do is you hold your nose and eat the spinach, because you couldn't taste it. Because what we say is taste is really smell.
So smell that comes from outside our nose up to the top of our nose, we call that smell. On the other hand, smells that come in through our mouth, go through the back of our throat up to our nose, we call that retronasal smell. We call that taste. And it's a form of synesthesia, of misperception of one sense as another. So for instance, if you close your eyes and you lightly push in your eyeball you see color when there's no color there. You're misperceiving the pressure as color.
ASHLEY HAMER: Those colors you see when you press on your eye are called phosphines, and some scientists think they could be real light your body's producing. The same way fireflies produce a glow. Generally though, it's believed that those lights happen because the pressure is making the cells in your eyes misfire.
ALAN HIRSCH: The same thing happens with smell and taste all the time. Smell outside our nose, we call smell. Smell that comes inside from our mouth up to the top of our nose, we call that smell, taste.
CODY GOUGH: And what is the reason for that? Are they wired to the same part of your brain?
ALAN HIRSCH: Well, exactly right. Ultimately, they go to the same part of the brain. What happens is that the smell component goes to our olfactory lobe, which is in the limbic system, but that's very closely related to the taste component. So when we have smell and taste, we tend to integrate the two together. But it's really smell that has such a major impact. So you can try and do this yourself. If you hold at your nose at home and eat vanilla ice cream, and chocolate ice cream, they'll taste identical. And they'll taste like vanilla.
So while there are other components that we perceive as flavor, it's really smell that's impacting upon it. And also there are all sorts of different emotions that are associated with smell. We began to look at this because we found that after people lost a sense of smell from head trauma or whatever, we found that a large number of them became depressed and anxious. And we thought, gee, if they become anxious when they lose a sense of smell, maybe there's some sort of free floating Valium in there that we're all smelling, and we lose your sense of smell, you can't detect it and hence you become more nervous.
So we studied different odors that could potentially impact upon anxiety. And we found that some odors, for instance, Jasmine for instance, and the trigeminal stimulants like citrus and peppermint tend to induce anxiety in people, and malodorous, unpleasant odors enhance anxiety. So when you're in a bad smelling place you become more anxious, and you become more aggressive, or angry. So for instance in days when there's a bad smell in air pollution, there's an increased number of motor vehicle accidents suggesting drivers are driving more aggressively.
In one study that was done many years ago, subjects were told by turning a knob to the right a colleague got an electric shock. In the presence of bad smell, they would turn the knob much further to the right. Or we studied a mulching site here in Illinois. And when there was a bad smell wafting across the street to the school, there was an increase in behavioral problems in the school children.
So all of this suggests that bad smells increase aggression. So what you want to do is to reduce aggression in your household, get rid of the bad smells and put pleasant smells there. You could even do one step further because you can actually use smells functionally in different rooms to have a positive effect. So for instance, if you want to be in the study and you want to study better, what we found is that in the presence of a mixed floral smell, 84% of the time there's an increase in speed of learning compared to no odor condition. So you can actually improve your speed of learning in the presence of a pleasant aroma.
CODY GOUGH: OK. Now, hold on a second. I want to know how this research is conducted.
ALAN HIRSCH: Oh, sure. Well, each study was done in different ways. And we have all sorts of different-- we have thousands of different odors here in the laboratory, and we look at them in all sorts of different combinations to see if they'll have a positive effect. And oftentimes, more often than not, we're wrong in their effects. But what we've done is, for instance, effects of odors in learning. We've studied this in adults. We study it in preschoolers, first graders, second graders, third graders, and high school students looking at effects of odors in learning.
And what we found is that odors actually improve speed of learning. When you look at something called the Trail Making Sub-Tests of the Halstead-Reitan battery, which is basically a connect-the-dot test.
CODY GOUGH: What is that test again?
ALAN HIRSCH: It's called the Trail Making Sub-Tests of the Halstead-Reitan battery. What it is is it's a-- it's you measure how fast they're able to connect the dots. And you do it three times you see how quickly they learn it. Most people are able to learn it very, very quickly. So we looked at normal's there, and we did it in the presence of different aromas. And we found that in the presence of mixed floral aroma they actually learned it much faster. And we found this to be true not only in children and adults, but we also looked in people who have minor learning disabilities, and it worked with them as well. However, one caveat is it had no impact if people could not smell.
And so if you can't smell it doesn't work, which makes some logical sense, because if you can't smell the odor won't have any effect. But that's one way that odors could potentially impact upon people. But what I would suggest to you is that odors impact upon us all the time. Let me give you another example. When we were looking at anxiety, and one of the hard things to study about anxiety is it's hard to make somebody anxious. And we were doing it and one of the subjects came up and said, I really-- could barely come in here because I have such strong claustrophobia when I go in an elevator, and he had impaired sense of smell.
And somebody else in the group said, you know what, same thing happened to me. After I lost my sense of smell, I became claustrophobic. So we began to think, gee, if you lose your sense of smell, you become claustrophobic. Maybe there's an odor in the air that's making us perceive the room as being larger than it actually is. So we studied the effects of odors on people's perception of room size. We put people in little coffin like tubes and closed the lid and measured the EEG, and measure heart rate, and all.
And what we found is in the presence of green apple smell and cucumber, they perceived the room as larger. And so in the presence of barbecued roasted meat, they perceived the room as actually smaller and more claustrophobic. So what you can actually do is you can actually change your perception of room size based on smell. So if you have a small room in your house, and you put cucumber there, or green apple smell there, people will perceive it's larger.
So for instance, if you have to sell your house, you want people to think the room is bigger than it is you can put those aromas there, and people will perceive it's a larger room. Or if you have to go on an airplane, and you can't stand being in small seats take some cucumber smell or green apple smell, and your perception will be its larger space.
CODY GOUGH: And where would you get a cucumber smell or a green apple smell?
ALAN HIRSCH: Oh, you can get that from any-- go to any grocery store, and you can get the shampoo. You get green Apple shampoo or cucumber shampoo put a few drops in a handkerchief for Kleenex and take a sniff at it.
CODY GOUGH: But you can't just sniff a handkerchief that it's got shampooed?
ALAN HIRSCH: Well, no. The smell will stay there for a while, or you can just get a little bottle of the shampoo and carry it around with you. But you can get these from-- literally there. You can get the scents-- the more expensive scents. Or you can just go buy shampoo, and they have the same effect. We know that trigeminal irritants make you more awake. These stimulants that make you cry when you cut an onion.
Similarly, we study the effects of odors on sexual arousal, and what we found is we measured-- we originally looked at this because we found that about a quarter of people after they lost their sense of smell developed sexual dysfunction. So the idea came up that there may be a relationship between odors and sexual arousal. And we're not the first ones to describe that. Freud, almost 100 years ago said that in order to remain a civilized society, we had to repress our olfactory instincts, otherwise we'd walk around sexually excited all the time.
So what we did is we looked and we met-- we took volunteer medical students, and we measured penile blood flow in the presence of all sorts of different floral smells, and perfumes. And as a control we threw in the smell of baked cinnamon bun. And lo and behold, the baked cinnamon buns had a greater effect than all the perfumes put together. So I wasn't sure what to make of that. It could just mean that medical students are always hungry, you don't know in that group.
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So we then studied males in the general population here in Chicago, ages 18 to 64. And we studied all sorts of floral smells, and perfumes, and a whole bunch more food items. And what we found is the number one, odor that enhanced penile blood flow was a combination of lavender and pumpkin pie. Number two, is a combination of donuts and Black licorice. And number three was a combination of pumpkin pie and donuts. However, there was individual variation.
So the older the man, the greater the engagement with vanilla. Those were most sexually satisfied had the greatest increase with strawberry. And those with the most frequent sexual intercourse had the greatest increase with lavender, oriental spice, and cola. And to give you an idea of what sort of changes those were. Perfumes increase penile blood flow by a median of 3% compared to 5% for cheese pizza, 9% for buttered popcorn, and 40% for lavender and pumpkin pie.
CODY GOUGH: 40%.
ALAN HIRSCH: That's right. And what was so interesting about this study was that for some of the subjects, they slept through the whole study. We'd be changing the odors, and we'd be measuring penile blood flow and they'd be sleeping the whole thing. They must have had sleep apnea or something. They are sleeping away. And despite being asleep, they still had the greatest impact in response to lavender and pumpkin pie.
CODY GOUGH: Is this why so many kids are born in July?
ALAN HIRSCH: Yeah. Well, we're not exactly sure why this is. And we had a number of hypotheses. But the biggest question we had was well if this arouses men, what arouses women. And the answer is we didn't know and no one had ever studied it. So we looked at it. We looked at vaginal blood flow in the presence of different aromas to see what odors enhance female sexual arousal. And we had basically two different hypotheses. On the one hand, we felt that it made no logical sense, no evolutionary sense for one sex to be aroused, while the other isn't. Therefore if food odors act to arouse men they should act to arouse women as well.
And we had a counter hypothesis, which is that since in our society women are often involved in preparation of food, which is not a very sexually exciting experience for them, food orders would act to inhibit sexual arousal. So we figured we had both bases covered. So we recruited women from City of Chicago in the And what we found was a number one odor that enhanced female sexual arousal had a combination of good and plenty and cucumber. Although good and plenty and banana nut bread also had very positive effects.
But we found differences between men and women. In men every single odor we tested enhanced penile blood flow suggesting that I guess men are easy to arouse. Whereas with women that wasn't the case. Some odors acted to inhibit sexual arousal.
CODY GOUGH: Really? Like what should they avoid?
ALAN HIRSCH: The smell of cherries. The smell of barbecued roasted meat and the smell of men's cologne, all acted to inhibit female sexual arousal. So it could be that cherries acted to inhibit because maybe it reminded people of taking cherry cough medicine as a child. Or men's cologne maybe reminded them of going out with some man, which was a negative sexual experience.
But I guess the bottom line-- if the aim of a man is to induce female sexual arousal, they should throw away the cologne and go get some good and plenty.
CODY GOUGH: Yeah. [CHUCKLES] They need to make a cucumber cologne, I guess. So you're basically saying that certain odors can turn us into superheroes? That it can enhance our learning, and it can enhance our sexual--
ALAN HIRSCH: One of the things we looked at was that they don't all have the same positive effect. We looked to see if an odor can enhance man's conversational ability, no effect. But we did look at empathy. And we looked at the idea that empathy could be impacted upon by aromas. And we found that a combination of eucalyptus, menthol, and camphor enhanced empathy in people.
So for instance, if you are going to want to talk to somebody, or if you're a psychiatrist, or if you're a therapist. If you wear those aromas, and sniff those aromas through the day, it'll enhance your empathy, and therefore ability to deal with others. Also one of the things we began to look at was it had to do with time perception. And this is sort of an interesting concept because the olfactory lobe is intricately associated with the areas of the brain involved with time.
And if you think about it for a second. When you go-- oftentimes I find that I'm going out on vacation, or whatever, or I have to give a conference and a second or two seconds before the alarm goes off, I'll wake up. Even though I've been asleep for hours. So the question is why is it that somehow there's some sort of unconscious clock that's going on all the time, whether we're aware of it or not that tells us what time it is. So the idea came up that well what's controlling that clock?
CODY GOUGH: Don't tell me it has to do with smell.
ALAN HIRSCH: Well, we tested that. That's exactly what we did. And we looked at the idea that at least while you're awake, odors could impact upon your perception of how long time is. And this is an area that's really not been studied at all. And the idea that this unconscious perception of time, whether we're wearing a watch or not, we always have a pretty good idea of what time it is. But the idea that you can even be asleep and in effect you can still have a perception of time is basically incredible. It's an area that people have ignored.
So what we found is that baby powder causes people to perceive time to be shorter. So if you have to wait, let's say, in a doctor's waiting room and you-- or if you have to undergo a painful surgical procedure like a bone marrow biopsy. If you have that smell of baby powder, you'll perceive the time as shorter and bothersome to you less. Alternatively, smell of cappuccino makes people perceive time as longer. So if you want to prolong an experience, if you have the smell of cappuccino there, people will perceive it lasted longer.
CODY GOUGH: You're talking about-- there's some compound recipes in here. Banana nut bread you said earlier.
ALAN HIRSCH: Yes.
CODY GOUGH: There's a lot of things in banana nut bread, and cappuccino. Are you able to isolate the dominant ingredient?
ALAN HIRSCH: Well, you're exactly right. And the answer is we have not. But you probably could if you had almost unlimited amount of time. Because in some and so often in the orders that we use there are many, many different notes.
ASHLEY HAMER: Scientists usually analyze the notes of a scent with something called gas chromatography. A detector that breaks a smell down into its component parts so that researchers can identify them.
ALAN HIRSCH: And it's usually the top three that people respond to, but it changes because there's something called adaptation. An adaptation is after you smelled something for a while, you can't smell it anymore, and then the other notes come out. So for instance, if you put on aftershave in the morning and you put it on, and you'll smell it. And then a few minutes later you can't smell it because your nose has adapted to it. Well, the same thing happens literally with everything we do.
When we're eating a food, if it's the same flavor, if we eat continually the same food, what happens by the last bite of the steak, you could substitute horse meat for it because you can't taste it because your nose has already adapted to it.
CODY GOUGH: So does that apply if you put a scent in a school, for example, wouldn't that happen to the students that day?
ALAN HIRSCH: Well, that's right. So what you want to do with that sort of thing, is you want to alternate or fluctuate the level of smell. So at times you apply it intermittently to give pulses of it so they can smell it. So you are 100% right. That it's just like when you put on your clothes in the morning and you feel it's nice and cold, or it's warm, or whatever. And then five minutes later you can't even feel them anymore. And you go through your day not even really feeling your clothes, unless you bring it up consciously, and then you'll think about it.
Well, the same thing as with smell. You will rapidly adapt because our nose has been based, or our sense of smell has been based evolutionarily on survival. You smell an odor of an attacker or of a lion that's about to attack you and you avoid it. So what happens, I always thought-- when I'm giving lectures to medical students, and they'll be yawning, I think, oh my goodness, they're yawning because they're bored.
What happens when you yawn, more odorant molecules enter your mouth and enters your nose, and you can tell if it's safe for you to fall asleep. And therefore, the lion is not to about to attack you. So therefore, they're yawning during the lecture to make sure that they're not going to be attacked.
CODY GOUGH: Are you saying yawning is caused by sense of smell?
ALAN HIRSCH: Well, yawning one of the reasons that yawning-- you think about why does yawning even exist? Why does it evolutionarily exist? It exists in humans. It exists in dog's. It exists in subhuman primates. And in other primates, why does it exist? Well, it's really interesting. One of the few things it does, is it brings more air in so you can detect more odors around you to make sure it's safe.
There's something else that happens with yawning, and that is there's a phenomenon that is communicable. So if I yawn you're more likely to yawn.
CODY GOUGH: Yawns are contagious.
ALAN HIRSCH: They're contagious and not only between people, also between people and dogs, and dog and dogs. So there is contagion in yawning. So I mean, but these are just some of the examples where smells can impact upon us, and they really impact upon all of our life in virtually every single way. For instance, one of the things we looked at, hand-eye coordination.
So we looked at bowlers and looked at effects of odors. We even looked at the Chicago White Sox and looked at their batting in the presence of different odors. And we found that a mixed floral smell actually enhanced batting performance. So you can actually affect people's physical activity based on aromas.
CODY GOUGH: All right, this mixed floral aroma sounds like a super scent. Where do I get it? What is this mixture of floral scents?
ALAN HIRSCH: You can get these mixed aromas. You can just go to the grocery store and get some shampoo, a floral shampoo. The exact mixture is probably not as important as the ultimate aroma. But there's different-- for different people there are different effects. And the other thing is because each of us has different abilities to smell.
And it even gets more complex than that because we know, for instance, that not only do women have better sense of smell than men do. But it depends upon where they are in their menstrual cycle. The time of ovulation their olfactory ability is the greatest in order to potentially detect any pheromones that might be present.
So there's a strong individual variation. And there are different things that people do to reduce sense of smell. For instance, cigarette smoking reduces sense of smell. And use of illegal drugs can impair it.
CODY GOUGH: One of my questions for you was where is the limit? What's the limit to all these superpowers because different scents can enhance your sexual arousal. It can enhance your athletic performance. It can enhance everything you've talked about. Is there anything it can't do?
ALAN HIRSCH: Well, absolutely. The problem where we are now is we know so little about smells impact upon people. We know much more about the moon than we know about smell. Smell has been an ignored sense. I mean, you go to your doctor's office and he or she may test your vision. Maybe test your hearing. But do they ever test your sense of smell?
CODY GOUGH: So how did you get into this then?
ALAN HIRSCH: Well, it was really two different reasons. One is I'm an obsessive sort of guy. And number two is I was too stupid to know better. And when I say that is first I did a neurology residency, and then I did a psychiatry residency. And being a very compulsive neurologist, I did a full neurologic exam on all my psychiatric patients and I found they couldn't smell. I said, oh my goodness. This is a way of understanding the biological underpinning of psychiatric disease. Maybe this is a window to the limbic system or emotions.
What I didn't know at the time was the reason they couldn't smell was because of the medications we had them on. And if I had known that, I would have probably gone on to study schizophrenia, or depression, or the like. Well, by the time I figured it out. I was already so well immersed in the field. I just continued.
CODY GOUGH: Wow. So what are the worst? You talked about some performance enhancing odors, essentially. What are the most inhibited odors that will just shut a person down or totally inhibit their abilities?
ALAN HIRSCH: I don't know. I know that if you give people unpleasant odors, malodorous, they increase aggression. They become much, much more aggressive.
CODY GOUGH: What's the most surprising finding to you that you've found over the years?
ALAN HIRSCH: There's so many that are interesting. One of the things that we looked at, is we looked at the effects of people's perception of weight. In other words, how much do you weigh? And what we did is we had a model wear a scarf around. And she would impregnate it with different odors and we'd have men estimate her weight. And we went to the Auto Show. We went to different bars. We had to stop going to the bars, because the men kept trying to hit on our model.
[LAUGHTER]
But what we found is that actually a mixed floral and spicy aroma actually made people perceive that the model was about 18% less heavy. Lighter in the presence of the odor.
CODY GOUGH: And which odor was that?
ALAN HIRSCH: This is a spicy mix floral. A spicy aroma combination. So what happens is that you can actually affect people's perception. Have you ever seen those pictures that looks like a-- on one side it looks like a duck, and the other side, it looks like a rabbit, or angels, and devils. Or even a Rorschach card, you can look at the pictures and you say, gee. Depending upon how they look, you can give a perception of their personality.
Well, we did that with smells. And so with smell you're able to change people's perception. Probably the most interesting studies that we've been doing lately have been looking at the idea that what you like to smell or what you like to eat can impact-- can indicate your underlying personality. So we looked at 18,631 people, and we gave them all sorts of different personality tests like the MMPI, the MCMI, the Beck, and the Zung.
ASHLEY HAMER: Wow, that was a lot of acronyms. The personality test he was referring to are the MMPI or the Minnesota Multiphasic Personality Inventory. The MCMI or the Millon Clinical Multi-axial Inventory. The Beck Depression Inventory and the Zung Self-Rating Anxiety Scale. Check out the show notes for more info on those.
ALAN HIRSCH: We were able to determine the personality type. And then we looked at their food preferences, and we correlated them together. So based on what food they liked, we were able to indicate what the personality was. We went one step further. We looked at the personality of the spouses, and we looked at what foods they like the most. And we were able to correlate them together.
So we looked at all sorts of foods, ice cream, snack foods, breakfast, cereals, meats, all sorts of things. But I can tell you the one that-- I don't have them all memorized. But I can tell you with-- for instance ice cream. Which of these six ice creams do you like the most, and here's your choices? Vanilla, double chocolate chunk, strawberries and cream, banana cream pie, chocolate chip, or butter pecan.
CODY GOUGH: At the risk of sounding boring, I'm going to say vanilla out of those options.
ALAN HIRSCH: Sure. Vanilla, and I would have thought vanilla was a bland boring personality. We found it was just the opposite. People who like vanilla are lively, energetic. They are the life of the party. They're anything but vanilla.
CODY GOUGH: I'm the life of the party, sweet.
ALAN HIRSCH: And they are most romantically compatible with others who like vanilla. Those who like double chocolate chunk tend to be very achievement oriented, aggressive individuals, and they tend to be most romantically compatible with those who like strawberries and cream. Those who like strawberries and cream tend to be irritable, cranky pessimists. However, those who like banana cream pie are empathetic, understanding, easygoing, well-adjusted, and they tend to be the universal romantic. They are compatible with everybody.
And those who like chocolate chip tend to be very social and understanding, and they're most romantic compatible with those who like butter pecan. And those who like butter pecan tend to be perfectionists. They have very strong ideals for themselves and others.
CODY GOUGH: All right, so what's the science behind this? Because this sounds a little bit like a quiz you would take on Buzz Feed or something. What's the ice cream personality?
ALAN HIRSCH: The science behind this is-- what we had done is we looked at these 18,631 people. We gave them all detailed psychiatric tests involving over 500 questions. We were able to determine the personality type and then we correlated their personality with their food preferences. And we're able to look at food preferences, and actually statistically find that they existed. To a large degree, we also looked at the spouses and saw what they liked. And we were able to correlate-- with the idea that if you've been married for over a year it indicated a stable romantic relationship and therefore you correlated those together.
Now, I have to tell you, there's some caveats to this. We did this in Chicago. So things that are true in Chicago may not be true where other food preferences are-- like for instance, it may not be true in Louisiana where there's different food types, or in Alaska, or some different subsections of the country. It's probably true for the Midwest and for other parts of the country where they eat a lot like we do here in Chicago.
CODY GOUGH: For example, if you did the test with hot dogs with ketchup that would be a problem in this city.
[LAUGHTER]
I don't think anybody would be compatible with anybody.
ASHLEY HAMER: The Chicago style hot dog includes yellow mustard, onions, neon green relish, a dill pickle spear, tomato wedges, sport peppers, celery salt, and absolutely positively zero ketchup. End of discussion.
ALAN HIRSCH: Well, there's another problem too, is that if too many people like the food we couldn't use it. So I mean, when we tried to just do plain chocolate, everybody liked it. So it didn't give us any statistical significance. So similarly, if everyone disliked it, it didn't tell us anything. Like rattlesnake, well, nobody likes it or very few people like it. So it didn't help us any. So we had to look at foods that a large number of people either liked or subsections liked.
CODY GOUGH: There's a confirmation bias that exists in a lot of people. The Barnum effect. I'm not sure if you have probably have heard of it before.
ASHLEY HAMER: The Barnum effect is named after the one and only PT Barnum. And it refers to the way people are willing to believe that things like psychic readings, fortune cookies, or any overly broad personality description is meant just for them, especially if that description is positive. Download the Curiosity app for Android or iOS to learn more.
CODY GOUGH: When you found out the results of your study, did you agree? Did you think that the ice cream personality-- but yeah, what was your favorite type of ice cream or do you not want to say?
ALAN HIRSCH: Well, I changed it since I knew the results. I said, all right, I'm going for the ice cream, that's the best one. That shows I've the best personality, and kindest, and so banana cream pie. But actually I probably would have gone with a double chocolate chunk. However, one of the things that we found is that there seems to be many of the different food groups tended to correlate together.
One of the things we thought is spicier foods would indicate maybe a spicy personality. We found it was actually the opposite. So one of the hypotheses we had was that maybe if you already have it in your personality, you don't seek it in your food. So people that like vanilla ice cream, they're already spicy. They already have a very vivacious personality so they don't have to seek it in their food. Now, that's a post-hoc analysis, and I'm really not sure why the findings we found were. It's just something that was statistically significant.
And we did this not just with ice cream. We looked at different vodka flavors, different toothpaste flavors. And there seemed to be a cross correlation. And let me tell you where this has come up useful for. We designed this originally for psychiatrists to use. So instead of using a Rorschach test to determine personality type, they could ask well, what's your favorite food type, and you could get a perspective then.
But we've had calls from employment agencies who wanted to use this. We even had a call from a trial attorney in California, who wanted to use this as part of his voir dire in jury selection to see who would be most sympathetic towards his client. I said, well, don't choose somebody who likes cheese puffs because people who like cheese puffs tend to be very dogmatic, and they view things all as black and white, and be more likely to send your client to the jail.
CODY GOUGH: Cheese puffs, really?
ALAN HIRSCH: That's right. And sort of-- but each subgroup there were different ones. So we looked at snack foods and we compared them to the different types of snack foods, potato chips, and tortilla chips, and that, and the like. So what it tells us is that it actually-- what we do, literally, every single thing we do reflects on our own personality. The direction we comb our hair. The color of tie we wear. The style shoes. Even the model of car we drive. The question is are we smart enough to figure out what it means. That's what we've done with some foods.
CODY GOUGH: And then we're going to need a lot more data to figure all this out.
ALAN HIRSCH: Oh, by all means. But if you think about it, literally, why do some people walk with their head down or some with their head up? Why do they look one way as opposed to the other? Our actions reflect who we are underneath, and that's what we've done with food. And ice cream makes a lot of sense because when you're choosing the ice cream you want-- as a kid your food preferences occur under the age of 5, ages 3 to 5.
And similarly, that's the same time your personality is developing. And people don't say to you when you go to the ice cream store, you have to have vanilla or you have to have chocolate. They let you choose. It's one of the first things you're allowed to choose. And so--
CODY GOUGH: Wow, you're right.
ALAN HIRSCH: And so it makes a lot of sense that these food preferences could indicate your underlying personality.
CODY GOUGH: If you asked me tomorrow or the next day, I might say strawberry. Because sometimes people will change.
ALAN HIRSCH: Well, you're exactly right. Although, if you look at things, sometimes people change because they've been told by their doctor don't eat this food or don't eat that food. We asked people not necessarily what they ate, but what they liked to eat. So many people would say, oh, I don't eat it because I'm on a diet, but I really like this food. So if you look at what they like or don't like, people don't change that much.
So for instance, when they go to a restaurant, they may want to look at the menu, but more often than not, they'll choose the same food each time. There's an inherent misoneism or a fear of the unknown, or fear of the new that individuals have. We also-- in food we call it this neophobia or fear of new things. And so people tend to stick with what they already know about.
CODY GOUGH: And there are a lot of people. There are people who will travel abroad, and go to McDonald's, and order the same thing off the menu.
ALAN HIRSCH: Oh, absolutely. And even when they travel abroad, they'll go to a restaurant, and then they go back to the same restaurant, they'll order the same thing. So if you look at-- if you go to a restaurant, next time you go out to eat in a restaurant, go to that same restaurant you ate, see if you ate the same-- if you ended up having the same thing you had before.
CODY GOUGH: I hope that your foundation is sending out this information to everybody because I feel like public policy globally should be dictated by what sense are present in certain places.
ALAN HIRSCH: Well, it clearly affects us. It affects our behavior in all sorts of different ways. When there's a bad smell present, no matter what, you can't prevent from smelling it and you tend to get more negative. And so if you want our politicians to be more cooperative with each other, put a pleasant aroma there and they'll be in half your state.
CODY GOUGH: There you go. We finally figured out the solution.
[CHUCKLES]
Well, for people listening, how can a person test his or her sense of smell?
ALAN HIRSCH: Oh, sure. There's all sorts of things you can actually do at home. One of the things you can do is take an alcohol pad and see if you can smell alcohol behind your chin. If you can smell it beyond your chin, it's probably normal. On the other hand, if you can't smell alcohol before it hits a bit closer to your nose, and your chin, it suggests there's an abnormality. You should talk to a doctor.
Other things like take food, ice cream, chocolate and vanilla, hold your nose and see-- don't even hold your nose. Just close your eyes and see if you can taste the difference between chocolate and vanilla. This becomes particularly important because when you lose your sense of smell, you're much more likely to be involved in gas explosions. So you don't detect the ethyl mercaptan that's added to natural gas to give it its gas like smell. So that's very important.
Also one of the other things is that you're more likely to be involved in food poisoning if you lose your sense of smell. So smell has a strong impact on safety, unhappiness, and health in general.
CODY GOUGH: It's maybe one of our greatest survival instinct, senses, then.
ALAN HIRSCH: Exactly. It was designed for survival. You knew it was safe to eat the food because you didn't get sick from it. You smelled your mother in utero and after birth. All of this is something that's involved for survival.
CODY GOUGH: Well, my final question for you is I would like to know what are you curious about, and I would like to challenge you? What are you curious about that you can tell me something that I don't know that's not related to smell?
ALAN HIRSCH: Oh, sure. Here's a good example for you. If you want to see well in the dark what food should you eat?
CODY GOUGH: If you want to see well in the dark. Well, the British said that you should eat carrots, but--
ALAN HIRSCH: Well, actually you're exactly right. But it wasn't. It was actually during the time of World War II and it's because they had a radar that could actually detect other Nazi planes and shoot them down. So they wanted to avoid the Nazis learning about it. So they said, OK, we will say it's carrots so they can see better at night times and protected their radar.
CODY GOUGH: Got it.
ALAN HIRSCH: But that's an example of something that we've all been taught as kids. Oh, eat carrots. Improve our vision. Well that's an example that actually what we think we know in reality is not true. And so many things we do are really not true. Just thinking about them of what we do and whether it makes a difference or not. And what I would suggest to you that all sorts of assumptions we hold now, if we actually explore them, we'll find that they're not the case.
CODY GOUGH: And now at this point you've told me all this really great information. So we're going to do a little Curiosity challenge. And I'm going to tell you something that perhaps you didn't know before that I think you might find interesting. Found this on curiosity.com. It's also on the Curiosity app available on the Apple App Store and the iTunes store, and Google Play store, and all those stores that are online. Did you know-- I don't know if you would know this-- roses smell different in space?
ALAN HIRSCH: Whoa. Well, that's great. I didn't realize that.
CODY GOUGH: In 1998 the company international flavors and fragrances sent them into space and the hypothesis was that the flowers oils because of the lack of gravity, it would keep the flowers oils in the stem, which would result in a different oil combination. So scientists collected these new essential oils that were produced as a result of the Rose being in zero gravity, and it's because of those oils the chemicals were different.
ASHLEY HAMER: Quick clarification. Gravity actually keeps the oils in the stem. So micro gravity helped them come out to produce those different combinations. Read the full article about this very cool experiment on curiosity.com.
CODY GOUGH: IFF actually bottled and commercialized the new fragrance so you can buy basically a zero gravity perfume. And there's a couple of those Shiseido zen, and a body spray, Unilever Impulse. And they both contain parts of the space rose.
ALAN HIRSCH: Well, that's great.
CODY GOUGH: So--
ALAN HIRSCH: Thank you. That's wonderful.
CODY GOUGH: Yeah, once we start to go to space there will be a whole new set of odors for you to analyze.
ALAN HIRSCH: Well, that's right. That's great.
CODY GOUGH: Will zero gravity Jasmine affect people more, or zero gravity lavender, and so many more possibilities. Your work will never stop.
ALAN HIRSCH: Well, you're right. You're right. There's a universe of smells to look at.
CODY GOUGH: Absolutely. Again this is Dr. Alan Hirsch with the Smell and Taste Treatment and Research Foundation. How long have you been doing this in Chicago?
ALAN HIRSCH: I've been doing this for about a quarter of a century looking at different smells. And I've written about a dozen books looking at different aspects of smell, and taste, and behavior, and health.
CODY GOUGH: Well, I know you said you have 100 more studies, we could talk about, and we would love to do that sometime. They're always interesting and fascinating, and I hope we can have more conversations. And always, please keep us posted on the latest and greatest.
ALAN HIRSCH: Oh thank you so much. It's been a pleasure. I'd be happy to.
CODY GOUGH: Wonderful. Great having you here. Thanks so much.
ALAN HIRSCH: Thank you.
[MUSIC PLAYING]
CODY GOUGH: I hope you enjoyed hearing from Dr. Alan Hirsch of the Smell And Taste treatment and Research Foundation. You can learn more about Dr. Hirsch's studies at smellandtaste.org. And remember to check the show notes for links to learn more about all the various subjects we covered today. You can also learn something new every day on curiosity.com.
And not everything has to do with smell and taste. For instance, did you know that solar paint can actually change your home into a clean energy source. Well, now you do. And the easiest way to learn more about that is to download the Curiosity app for your Android or iOS device.
Speaking of additional information, I'd like to thank Ashley Hammer for her fast, facts and I'd like to Thank you for listening. And if you enjoyed this episode then please give us a quick review and rating on iTunes or wherever else you streamed this podcast, and I hope you will join me next time. For the Curiosity podcast, I'm Cody Goff. Have a wonderful week.